With the rise of aging society, the number of patients with degenerative brain diseases, such as Alzheimer's disease, Parkinson's disease and dementia is rapidly increasing. Alzheimer's disease, the most common degenerative brain disease that causes dementia, slowly develops and gradually deteriorates cognitive functions including memory. While the exact cause of Alzheimer's disease has yet to be found, it is closely associated with aging and is growing with the increase of the older population.
Parkinson's disease is a chronic progressive degenerative disease of the nerve system caused by the loss of dopamine neurons, showing symptoms of muscle cramps, bradykinesia (slowness of movement) and postural instability. Patients with Alzheimer's disease show symptoms of dementia, such as speech impairment and executive function inability while patients with Parkinson's disease show symptoms of dementia, such as lapses in concentration and visual/spatial judgment, executive function disorder and slowness in thinking.
Dementia may be defined as a condition where a physically stable person experiences damage to brain function due to various causes and gradual deterioration of the overall cognitive ability, greatly affecting daily life activities. Cognitive ability herein means various intellectual abilities, such as memory, speech, visual-spatial ability, judgment and abstract thinking. Each of the cognitive abilities is deeply associated with a certain part of brain. About 50% of dementia are a Alzheimer's disease-type, 20 to 30% of dementia are a blood vessel-type and there are other types of dementia, such as alcohol-related dementia, dementia with Lewy bodies, frontotemporal dementia, and Parkinson's disease dementia. Recently, there have been studies that various degenerative brain diseases including dementia are associated with Intestinal Permeability Syndrome or intestinal flora disturbance.
Intestinal Permeability Syndrome and Dementia
The gastrointestinal tract of the human body is composed of mucus and villi, which efficiently absorb nutrient components, but prevent the absorption of pathogenic microorganisms having a high molecular weight or toxins produced by these microorganisms. In addition, the human body has an immune system capable of protecting the body from invasion of external antigens having a high molecular weight. However, due to infection with many pathogenic microorganisms or toxins, excessive stress, intake of foods such as high-fat diets capable of proliferating harmful bacterial living in the gastrointestinal tract, excessive alcohol intake, the abuse of drugs (e.g., antibiotics) and the like, intestinal flora is disturbed, abnormalities in the gastrointestinal tract's immune system occur, and expression of tight junction proteins is inhibited. If expression of tight junction proteins is inhibited, tight junction of intestinal mucosa becomes loosened, and the invasion into the body of large molecules due to the loosened gap and abnormalities in the immune system. Intestinal permeability syndrome is also known as leaky gut syndrome, and refers to a condition in which external such as less digested foods, pathogenic microorganisms, toxins or the like are continuously introduced into blood, because the tight junction barrier system of epithelial cells forming the gastrointestinal tract is not smoothly operated. When intestinal permeability syndrome occurs, external antigens that are generally not absorbed into the body enter the body, thus causing ulcerative colitis, Crohn's disease, liver injury, liver dysfunction, allergic diseases (including asthma), atopy, autoimmune diseases, steatorrhea, digestive absorption disorder, acne, accelerated aging, endotoxemia, intestinal infection, eczema, irritable bowel syndrome, chronic fatigue syndrome, psoriasis, rheumatoid arthritis, pancreatic insufficiency, inflammatory joint diseases or the like. Recently, there have been studies that Intestinal Permeability Syndrome is associated with dementia caused by Parkinson's disease or aging.
Intestinal Flora Disturbance and Dementia
There are many bacteria living in the gastrointestinal tract of the human body. The human body has about 10 trillion normal cells, but has about 100 trillion bacteria which are about 10-fold larger than the normal cells. These bacteria may be divided into beneficial bacteria that help human intestinal health and harmful bacteria that are harmful to human health. The health of human body may be maintained when beneficial bacterial such as Lactobacillus, Bifidobacterium, Streptococcus, Leuconostoc, Pediococcus, Sporolactobacillius and the like are more dominant in the gastrointestinal tract than harmful bacteria. Otherwise, diseases may be caused, such as obesity, intestinal permeability syndrome, liver diseases, accelerated aging, enteritis, accelerated aging, dementia and the like. Increase of harmful microorganisms in the intestinal flora (ex. Klebsiella pneumoniae, Escherichia coli, Proteus mirabilis, etc.) boosts the activity of NF-kB in intestinal cells, which can dramatically increase the possibility of degenerative brain diseases, such as Alzheimer's disease and Parkinson's disease, and dementia.
Probiotics are collectively referred to as live microorganisms that improve the host's microbial environment in the gastrointestinal tract of animals, including humans, and have beneficial effects on the host's health. In order to be effective as probiotics, it is necessary to have excellent acid resistance, bile resistance and adherence to epithelial cells, because most of these probiotics should reach the small intestine upon oral administration and must be adhered to the intestinal surface. Lactic acid bacteria are used as probiotics because they play a role in decomposing fibrous and complex proteins to make important nutrients while living in the digestive system of the human body. Lactic acid bacteria have been reported to exhibit effects such as maintenance of intestinal normal flora, improvement of intestinal flora, anti-diabetic and anti-hyperlipidemic effects, inhibition of carcinogenesis, inhibition of colitis, and nonspecific activity of the host's immune system. Among these lactic acid bacteria, Lactobacillus sp. strains are major members of normal microbial communities living in the bowel of the human body and have long been known to be important in maintaining a healthy digestive tract and vaginal environment. Currently, according to the U.S. Public Health Service guidelines, all the Lactobacillus strains deposited with the American Type Culture Collection (ATCC) are classified as ‘Bio-Safety Level 1’, which is recognized as having no known potential risk of causing disease in humans or animals. Meanwhile, lactic acid bacteria of kimchi that are involved in kimchi fermentation have been reported to have immune enhancement effects, antimicrobial effects, antioxidant effects, anti-cancer effects, anti-obesity effects, hypertension preventive effects or constipation preventive effects [Hivak P, Odrska J, Ferencik M, Ebringer L, Jahnova E, Mikes Z. One-year application of Probiotic strain Enterococcus facium M-74 decreases Serum cholesterol levels: Bratisl lek Listy 2005; 106(2); 67-72; Agerholm-Larsen L. Bell M L. Grunwald G K. Astrup A.: The effect of a probiotic milk product on plasma cholesterol: a metaanalysis of short-term intervention studies; Eur J Clin Nutr. 2000; 54(11) 856-860; Renato Sousa, Jaroslava Helper, Jian Zhang, Strephen J Lewis and Wani O Li; Effect of Lactobacillus acidophilus supernants on body weight and leptin expression in rats; BMC complementary and alternative medicine. 2008; 8(5)1-8].
Since various bioactive activities of lactic acid bacteria were known, There have recently been a growing number of studies designed to develop a safe and highly functional lactic acid bacteria flora for the human body and turn it into an ingredient of medicinal products or functional foods. For example, the Korean Patent Gazette for registration No. 10-1476236 discloses a pharmaceutical composition for prevention or treatment of dementia, comprising lactobacillus pentosus var. plantarum C29 KCCM11291P flora as an active ingredient. The Korean Patent Gazette for registration No. 10-1087972 discloses the preparation method of lactic acid bacteria ferment that is effective in preventing and treating dementia, comprising (a) a stage to inoculate, culture and ferment lactic acid bacteria selected from lactobacillus sp., enterococcus sp. and bifidobacterium sp. into the medium comprising milk; (b) a stage to remove lactic acid bacteria from the above ferment; and (c) a stage to precipitate separate active ingredients adding a solvent selected from a group consisting of acetone and alcohol having 1 to 6 carbon atoms to the ferment, which had lactic acid bacteria removed. In addition, the Korean Patent Gazette for registration No. 10-1424547 discloses a pharmaceutical composition for preventing or treating degenerative brain diseases comprising the lactic acid bacteria ferment of Lactobacillus fermentum KFRI 164 of Sibjeondaebotang, as an active ingredient. Also, the Korean Patent Gazette for publication No. 10-2015-0047687 discloses a composition for preventing or improving forgetfulness or improving memory, comprising the plant extract that was fermented by adding 0.1 to 10 wt % of glucose and 0.1 to 5 wt % of yeast extract to a plant extract, hot-water extracted from Polygala tenuifolia, white Poria cocos Wolf, and Acoris gramineus, and then inoculating the cultured Lactobacillus plantarum. 
And yet, lactic acid bacteria disclosed in the prior art or the product fermented by the same is not enough to be applied as a commercial treatment since it is not highly effective in treating degenerative brain diseases including dementia. As such, it is necessary to screening a certain type of lactic acid bacteria that has the equivalent level of treatment effect for brain diseases compared to commercial treatments, and improves Intestinal Flora Disturbance and Intestinal Permeability Syndrome, thereby developing medicinal products or functional foods.